xAnnixx

"An unknown compound, X, of molecular formula C4H8O2, has the following IR,  H NMR and MS spectra. Deduce the structure of X using the information given and 
any other additional information from sections 26–28 of the data booklet. For each spectrum, assign as much spectroscopic information as possible, based on the structure of X."

About this question. I'm easily able to find things like the IHD and the wavelengths given in the spectrum that's presented. I found out there is a carbonyl group and a C - H bond.

I was wondering if someone knew how to deduce relative integration numbers either from this question or from a H NMR spectrum. I can see that there are three signals, but I'm not sure how to deduce the integration numbers from the spectrum or the given formula? Any help would be appreciated

"Compound Y is a hydrocarbon and has a molar mass of 86.20 g mol–1. Upon combustion, Y produces 1.75 g CO and 0.836 g H2O.
Deduce the molecular formula for Y."

This is a question I tried solving yesterday, related to Stoichiometry. It's simple enough and I understand the general way to solve this. After calculating both n(C) and n(H), I tried calculating n(C)/n(H). My problem is that this resulted in something like this: 

0.0398/0.0928 = 199/464 (=0.4288...)

The solutions that are available to me say it's more like 3/7. Now, my question is probably more related to math and calculators than chemistry itself. I can't seem to get this approximation of 3/7 with my TI - Inspire calculator. It just gives me the fraction shown above with an approximation of the decimals. Is there some sort of trick I can use mathematically, or should I be able to tell just by looking that it is around that average. A more universal method would be appreciated.